Acta C/~-"ciaIndica. Vol. XIllP.,No. 1. 6 (/987)

, 1HYlJh: Ill]!;::.> uN ~;Lb:C'I'li:uNb.;(~A'1' J Y 1 'l'Y

VIRENDRA KUMAR JAINAND

Z. H. ZAIDIDEl-'AkTl1EN'l' uJ-t' IJH Y!3 1 C::':;

JAMIA MILLIA [~LAMIAJAMIA NAGAR. NEW DELHl-l1UU~~

INDlA.

Received: 26 May,

The empl r-LoaI reJClLion

proposed by us r 1 I has bef-!Il extended Lo

calculaLe. vilJratiowd ~l e for(HnLO/lli(~ hvdr i de s . x~ , xfl and nfl' »» are Lhf:'

elf!ctre,negati vi ties and the number of va l errc e

el(,~ctru!J~; .fir constituent atoms A and B

r~s~ectively. K is a constant for each group or

subgroup ofi~he periodic table and f. is the. .

reduced mass o~ the molecule AB. The results

obtained .usi rIg the new relation are in better

agreement w i Lh the experimental va l.ue s than

Lho::-;e 0/>1,;1 i Jlf:!d f:!ar1i er by Huxaa i r, f? r .

t', .'{:> f.,.. '_0 .

2

A number of worKers r3-6] have shown that ~he/

reduced mass f and the electronegativity may play dn

important role in the calculation of vLbrat.Lona I constant tI)e/

of· diatomic molecules. Krasnov and Maksimov [7] pointed

out that exact dependence_of We on the reduced mass, must

take into account the type of chemical binding between

the constituent atoms of the molecule. However, the

relation suggested by them do~s not appe~r to contain any

molecular parameter which could b~ said to depend upon

chemical binding.

It has been ~hown th~t the vibrational frequencyof a diatomic hydride A-H should have a linear relationship·

with the electronegativity of A [8,9,lU]. This deductiun is

obvious from the fact that during the vibration of a

hydride molecule, displacement of the hydn.J~F;n wOlll.d in

turn cause a displacement of the valence e Lect.rons in the

potential field of the heavier atom. In a vibrat.o ry 1.ink

A~H , both A and H are displaced with respect to the centre

of gravity of the bonding electron cloud. Gordy allll

Thomas [llJ concluded from this, that in a diatomic

moleculeWt! = f ,( x A . x (3) _.r--: - - •• - - - - - - •• - - - - - - - - ( 1)

where f ( Xftxf3 ) is a function of the product xfl xfJ.,

3

Recently, the present authors suggested that the

valence electrons should also .be taken into account while

considering the nature 'of/chemical bonding in between the

consti tuent atoms and We Sh~d be taken as a function of

the product of the electronegativities and the number of

valence electrons of the constituent atoms. The suggested

relation was

We = K ( x t1. n[y x[3 nR ) /Jf --------(2)

where K was a constant for each group or subgroup of the

perLod Lc table', n A' nf3 were, the number of valence electrons

associated with atoms A and. B respectively. We call the

product ~A .nf3 as the "Valence Force" acting between atom

A and valence electrons nB The relation gave fairly good

agreement with the observed values whe'n used to calculate

~'e for diatom~c oxides.Ln an attempt to see the validity of relation (2)

for other molecules, we ,have applied it to compute the

values of We for diatomic hydrides. The resGlts which

are in better agreement with the experimental values as

compared to earlier work, are being reported in the present

note.

The calculated Mld experimental values wherever

available, are compared in Table -1. The ,values of I ,. for'-Vet

some diatomic' hydrides which have not been,)

studied

e~periment~lly so far, are predicted. It is clear fromI

TKbl-=:-1 t.lt~1t the ;';H?reement t·'~tween t.,hf.~ values of W observe.Ie.

4

TA,i?J.kL COMPARISON OF OBSERVED AND QALC!l1AIEP. Yl~RAIIONA1---'-GQN~iiMrl?-'(t-C-iiii-gID-11-'- -- -_._- '------------------------------------~-----------------------~-~--~-Group~

'. ~ Q~lgy!~t~g" Q~§~~y~gbaEE~Q~~~ K~~Ql,Molecule Electro- Authors Hussain or Authors Huasaan

-negativity estimated--------------------------~---------------------------------------------------_.HH 2.1

LiH 1.0 1405.65 1412 14D5.65 0 -litI A NaH 0.85 1141. 48 1160 1172.2 +3 +1(1) KH 0.74 985.16 1014 983.6 0' -3

K=628.35 RbH 0.7 925.53 936.7 936.9 +1 0CsH 0.69 910.38 872.0 891. 2 -2 +2

BeH 1.6 2058.6 2036 2058.6 0 +1II A '.MgH 1.2' 1494.69 1496 1497.0 0 0,,(2) .CaH 1.06 1309.63 1221 1299.0 -1 +6

K~291. 66 SrH 0.98 1202.64 1201 1206.2 0 0BaH 0.97 1187.92 1172 1168.31 -2 0

BH 2.0 2248.96 2617 2366.9 +5 -11III A AIH 1.5 1644.32 1683 1682.56 +2 o '~

(3 j GaH 1.48 1604.52 1775 1604.52 0 -11K=17151 InH 1.36 1470.17 1545 1476.0 +1/2 -5

TlH 1.34 1445.78 1532 1390.7 -4 -10

CH 2.6 2859.1 2862 2859.1 0 0IV A SiH 1.9 2042.60 1966 2041.8 0 +4

(4) GeH 1.8 1914.43 1825 1908 -1/2 +4K=126.23 SnH 1.6 1696.99 1750 1715 +1 -2

PbH 1.5 158e.13 1641 1564.1 -2 -5

NH 3.0 3203.2 3300 3203.2 0 -3V A PH 2.2 2305.40 2107 [2380]1 +3 +12( 5 ) AsH 2.0 2076.36 1925 [2037 ]ei -2 +6

:# K=98.60 SbH 1.8 1864.00 1804 [1866] 0 +3BiH 1.7 1757.38 1698 1698.9 -6 0

OH 3.5 3739.94 3735 3739.94 0 0VI A SH 2.53 2663.10 2700 2689.6 +1 0

(6) SeH 2.3 2398.71 2481 [2400)l 0 -3K=82.58 TeH 2.0 2080.83 2194 [2073] -1/2' -6

FH 4.0 4032.17 4243 4138.32 +3 -3VII A CIH "3.0 2989.14 2990 2990.94 0 o \,

(7 ) BrH 2.68 2648.98 2635 2648.98 0 +1/2K=67.09 IH 2.36 2327.47 2309 2308.09 -1 0

AtH 2.2 2166.11 2009 [2138]cl -1 +6

TABLE-1 : .continued......IS

VIII NiH' 1.8 2000 2000 0 -(10) f'dH 2.0 2213.36 -K=52.66 f'tH 2.1 2319.2'1 r2293.6JC -1

I B CuH 2.0 1940.4 1940 1940.4 0 0(11 ) AgH 1.8 1'r40.69 1826 Ho9.9 +1 -4K=41.83 AuH 2.4 2315.96 2305 230b.01 -1/2 0II B ZnH 1.7 Hi07.6 1608 1607.6 0 0(12 ) CdH 1.5 1413.63 1433 1430.7 +1 0K=37.38 HgH 1.5 1410.93 138'1 '1387.09 -2 0

----------------------------------------------------------------------------~*-Numbers within parentheses are the number of valence electrons and K 1s a,..

constant for each group. -a-Collected from Pritchard and Skinner, Chem.Revs., 55, '145 (1955); Gordy and

. Thomas. J.Chem.Phys .. 24, 439 (1956); Allred and Rochow, J.Inorg.Nucl.Chem.5, 264 (1958); Mulliken, J.Chim.Phys. 46. 497 (1949)

b-Taken from American Institute of Physics Handb00k, McGraw Hill Book Co ..Third edition (1982) and Huber and Herzberg, Molecular Spectra andMolecular Structure IV. Constants of Diatomic Molecules, Van Nostrand Co.Newyork (1978),if not indicated otherwise.

c-Values are uncertain.d·.Values estimated by Sheline (1950) and Varshni (1958)

and those calculated with relation-(2) is better. in general,

than the previous calculations made by Hussain [2]. The maximum

deviations between the 9alculated and experimental values

are about 6% for BH and BiH. Spectra for these molecules have notbeen studied in absorption [12] and if the observations are made

only from studies in emission, one cannot be completelysure whether. the observed values represent those of the ground

...state or not. Values of UJe predicted from relation (2) for the

molecules AsH. SbH, TeH and AtH are in good agreement with

the values estimated from the force constants obtained by

Sheline [13] and Varshni [14].

REFERENCES

[1] Jain, V.K.;Mishra,A.K.and Zaidi,Z.H.;Acta Ciencia Indica 12 •.80(1986 ).

[2] Hussain, Z.; Can. J. Phys. 44, 917 (1966).[3] Hussain, Z.; Can. J. PHys. 43, 1690 (1965).[4] Goodfriend, P.L.; Can. J. Phys. 45,3425 (1967).[5] Singh,S.P. and Mathur,V.K.;Indfan J. Pure Appl. Phys.

I

1·: '6,38'6.(1968).- \. .

[6] Sharma,K.K. and Hussain,Z.; Indian J. Pure Appl.·Phys,'.7,662 <,1~89-\ .

[7] Krasnov, K.S. and Maksimov, A. I.; Optika Spektrosk; 8,403 (fs.e0).[8] Pauling,L.; The Nature of the Chemical Bond, Cornell univerSi~

.Press, Ithaca,New York; 58\75 (1939~[9] Walsh, A.D.; Proc. Roy. Soc. 207 A, 13 (1951).

[10] Wilmshurst, J.K ..; J. Chem. Phys. 28,733 (1958).[11] Gordy, W. and Thomas, W.J .0.; J. Chem. Phys. 24, 439 (1956). '-..

![12] Herzberg,G.;Spectra of Diatomic Molecules;D.Van Nostrand Co.Inc.(1950).

[13] Sheline, R.K.; J. Chem. Phys. 18, 927 (1950).[1.] V~shni, Y.P.; J.Chem. Phys. 28, 1081 (1958).

tI